A new study (pdf) in the Nov. 14 issue of The Journal of Neuroscience showed that men in relationships that were given the hormone oxytocin were more likely to want to stay farther away from an unknown woman they found attractive, compared to single men given the hormone or men that took a placebo…

“Previous animal research in prairie voles identified oxytocin as major key for monogamous fidelity in animals,” Dr. Rene Hurlemann, a psychiatrist University of Bonn in Bonn, Germany, said in a press release. “Here, we provide the first evidence that oxytocin may have a similar role for humans.”